As soon as it became apparent what the stakes would be, Mathias Kiwanuka knew this game had to be flexed to the evening, given a national spotlight.

“It’s the big one, this is the one people want to see, for good reason,’’ the Giants linebacker said. “To be able to play at home, against a divisional opponent that is a rival and hated as much and have everything on the line, it’s us or them, that’s one of the biggest stages in the regular season.’’

The NFL saved the best for last in the final regular-season game of the 2011 season. No, the Giants and Cowboys, both 8-7, are not the best the league has to offer, not by a long-shot, but that’s a debate for another day. The winner claims the NFC East title, gets the No. 4 seed in the NFC and a home playoff game next weekend. The loser is 8-8 and packs it up, a very unhappy New Year. The Giants tonight will distribute white towels emblazoned with their new slogan – “All In!’’ – for what is the most significant game in the two-year history of MetLife Stadium. It is also, according to the Giants, the first regular-season finale in their 87-year franchise history with clear-cut win-and-in, lose-and-out playoff ramifications.

“I hear from older guys all the time, playoffs are hard to come by so when you get the opportunity, take full advantage of it,’’ receiver Hakeem Nicks said.

Any playoff-elimination bout is high drama but that it’s the despised, rival Cowboys standing in the way of the Giants adds spice to an already savory mixture. Losing to the Jets last week would have pained the Giants. Getting ousted by the Cowboys, in the Giants home, would be an unbearable indignity.

“It’s going to be a battle,’’ defensive tackle (and former Cowboy) Chris Canty said. “You have to play the game with extreme emotion, extreme passion. The Xs and Os are important but you have got to play from the heart. This time of year you have got to play from the heart.’’

The Giants are hoping home is where the heart is.

A look inside the game:

BEST BATTLE

Cowboys NT Jay Ratliff vs. Giants C David Baas. One of the main reasons why the Cowboys are seventh in the league in run defense (allowing 98.6 yards per game) is the sturdy work inside by Ratliff, who this week was selected to the Pro Bowl for the fourth time. Baas, completing an injury-filled and disappointing first year with the Giants, returned last week after missing three games with a neck injury and looked rusty before settling in.

HAND IT TO TONY

All eyes will be on the bruised right hand of Tony Romo, attempting to detect any sign that he’s not gripping the ball or throwing it with his usual gusto. Three weeks ago, Romo had no difficulty shredding the Giants’ shaky secondary for four touchdown passes in a 37-34 Giants victory and he’s actually had an under-the-radar great season (29 TDs, nine interceptions). As the Giants know all-too-well, Romo is most dangerous when he’s improvising.

“The reason why you want to keep him in the pocket is he’s not tall and he has a big, tall offensive line and it makes it a little bit more difficult for him to see downfield when he’s in the pocket,’’ Justin Tuck said. “He’s very crafty and kind of baiting d-ends to come rushing inside and he kind of does that spin move, especially to his right to get outside. It’s all about being aware.’’

UP FRONT THAT COUNTS

The Cowboys’ hirsute defensive coordinator, Rob Ryan, hasn’t been able to cover up his unit’s deficiencies on the back end but he has an outstanding front group. Ryan will present the Giants offensive line with “rolling fronts’’ designed to cause confusion. “That’s been kind of like his deal,’’ left guard Kevin Boothe said. “We look at the ‘fronts’ page as far as how many different defenses they play and it’s the whole page. You can’t get used to or expect one defense.’’

WASTE NOT

Everyone around the Giants realizes Eli Manning has put in his career-best season — his finest moment was his two touchdown passes in the last 3:14 in Dallas — but he has taken a statistical dive the past two games, completing only 48 percent of his passes to go along with only one touchdown pass and four interceptions. Manning’s targets are hobbling, with receivers Hakeem Nicks (hamstring) and Mario Manningham (knee) not at full strength and tight end Jake Ballard (knee) out. Can Manning yet again initiate (Victor) Cruz Control? The wondrous Cruz was brilliant last week against the Jets and may have to carry the load once more.

OPEN SEASON

It was an incredible sight, Dez Bryant uncovered deep down the field, completing a 50-yard pass play for a touchdown to put the Cowboys ahead 34-22 late in the fourth quarter, with Corey Webster, Antrel Rolle and Deon Grant not making a move. The Giants came back to win but the troubling memory of a blown coverage still lingers. The Giants secondary believes it has solved the lapses that award gift points to the opponent.

“It was really embarrassing when you come back and watch film and watch the TV copy and see the mental busts on the back end,” cornerback Aaron Ross said. “So we got together as a unit and told each other we can’t have that happen again.”

UNDER COVER

For the first time in eight years, Cowboys tight end Jason Witten was not selected to the Pro Bowl. Still, he’s the runaway team leader in receptions (72) but his least productive game (three catches, 12 yards) all season came against the Giants, as rookie linebacker Jacquian Williams had his best game dropping in coverage.

“They didn’t throw him the ball, whatever the reason was I don’t know,’’ Williams said. “I felt like I had good coverage but if you know him it’s always like that and they still throw it to him and he catches it. Maybe someone else was open.’’

Paul’s prediction:

Sentiment nationwide seems to be that the Cowboys are finished, kaput, not primed for a big performance. Why not? Unless Tony Romo is truly hurting, his offense presents multiple problems and the Giants haven’t put back-to-back defensive efforts together all season. Unless Eli Manning gets cooking early and the crowd takes over, settle in for an all-nighter.